Facebook today announced it is testing a new feature with ‘a few’ small and medium-sized businesses in the US: a Buy button. The goal is to help businesses drive sales directly through Facebook via News Feed ads and Page posts.

The button is available to users on the desktop site as well as on mobile. In short, it allows them to purchase a product or service from a business, without ever having to leave Facebook.

Here’s how it looks:

Facebook says the feature is built “with privacy in mind” and that the payment experience is “safe and secure.” The company promises the credit card or debit card information you share with it when completing a transaction will not be shared with other advertisers. Saving payment information for future purchases is available, but is completely optional.

This is a big deal for Facebook: the company could not only open up the gateway for amassing user payment information, but it could expand its role as a marketing platform. Currently, all the ads served on Facebook are aimed at building a following, driving traffic, or getting customers to a physical location:

Clicks to Website

Website Conversions

Page Post Engagement

Page Likes

App Installs

App Engagement

In-store Offer claims

Event Responses

If Facebook can get ads to convert into sales directly on its site (and that’s a big if; there’s no indication users will be necessarily interested), it will be a huge boon to its bottom line. The reason the company is starting out small (only select businesses in the US) makes sense: this is a very important trial, and one that will likely go through several iterations to verify its overall potential.